Gnome 3 has just made it into Debian experimental with version 3.0 packages available, but once you have installed this you will have great problems getting back to Gnome 2.32, so it is not recommended to install this until the packages are perfected and the panel applets such as the Weather and CPU speed applets are ported to Gnome 3. I have heard that Debian Testing/Sid has the Gnome 3 packages now, this means that version 3.2 of the Gnome Shell could be in Experimental soon, as it is better than version 3.0. The thing I noticed when I tested out the Gnome 3 desktop on Fedora 15 was that you could not customise the desktop as much as you can with Gnome 2.32 or even Gnome 2.30. I am running Debian Stable with Gnome 2.30.2 and this desktop environment is perfectly suitable for day to day usage and it does not need a totally different desktop interface to be usable. So the challenge for the Gnome developers is to make the Gnome 3 desktop environment a very easy to use and customise desktop that is perfectly usable and has all the popular Gnome Panel applets that version 2 of Gnome featured.
We will wait and see what happens with this different new desktop GUI. Ubuntu 11.10 uses this desktop and Debian seems to be following in their stead, so we will have to get used to it when a future Debian installation with Gnome will install version 3 instead of the familiar Gnome 2.32.